Assay-furnace.



'PATBNTED 11119.22, 1905.

A. M. MAGDUFFEE.

ASSAY FURNAOE.

APPLIGM'IQN FILED MAR. 7, 1905.

witness AMOS M. MACDUFFEE, OF OHLORIDE, ARIZONA TERRITORY.

ASSAY-FURNACE.

Specification of Letters Patent'.

Patented Aug'. 22, 1905.

Application filed March '7, 1905. Serial No. 248,845.

To all whom, it may concern:

Be it known that I, AMos M. MACDUFFEE, a citizen of the United States, residing' at Chloride, in the county of Mohave Vand Territory of Arizona, have invented new and useful Improvements in Assay-Furnaces, of which the following is a specification.

My invention relates to certain new and useful improvements in that class of furnaces particularly designed for assay-work and wherein the furnace is of a simple portable type and wherein liquid or gaseous fuel may be used for obtaining the requisite heat, and

the utmost facility is afforded for the insertion, removal, or repair of the muflie; and lmy invention consists of the parts and the constructions and combinations of parts, which I will hereinafter describe and claim.

In the accompanying' drawings, in which similar letters of reference indicate like parts throughout the several views, Figure l is a perspective view showing the front of the furnace removed and showing the removable bottom of the muffie in position ready for cupeling. Fig. 2 is a perspective view with the front and rear sides of the furnace removed, showing the bottom fiue or channel and fuelinlet and showing the bottom 0f the muffle removed and crucibles along one side of the muffle. Fig. 3 is a longitudinal sectional view of the furnace. Fig. 4 is a cross-sectional View of the furnace on the line w w of Fig. 3.

In Aconstructing my furnace I have kept in View its availability for the prospector, mine examiner, and general assayer. Therefore I have made it as light as practicable to insure its being readily transported substantially in the manner of the usual hand-Satchel. The general dimensions of the furnace may vary, of course; but a total length of about fifteen (15) inches, a width of about eleven and onehalf (11%) inches, and a height of about nine (9) inches will be sufiicient for the ordinary purposes for which the furnace is designed. v

The general design of the furnace does not depart essentially from some of the assayfurnaces in use in that it has a mufiie the general configuration of which and of the outer casing of the furnace is dome-shaped.

Referringnow to the drawings for a more complete understanding of the furnace, A represents'a sheet-iron or other outer covering interior to which and protected thereby is arranged an asbestos or other suitable lagging B. Within this lagging is an inner lining composed of fire-clay or other heat-resisting material of about one-half (tlinch in thickness, more or less.

.The bottom O of the furnace and likewise the front and back ends are composed of fireclay or equivalent material, the said bottom being, say` one and one-half (it) inches thick and the said ends about one (l) inch thick in a furnace of the dimensions first above given, while the hearth-piece may constitute a furthe extension of the bottom of about one (l) inc Within the fire-clay lining and conforming to the general shape thereof and separated therefrom a sufficient distance-say about one quarter inchto form aflue or passage a between the two is the muflie D, composed of fire-clayV or equivalent material'of about one-quarter' inch in-thickness. This muffle consists of the arched top and the sides and a rear end. It is open at the front end and is made without a fixed bottom, thus adapting the furnace for melting in crucibles, as shown in Fig. 2, or for cupeling. as shown in Fig. 1.

To facilitate the melting operation and also the operation of cupeling, which I will hereinafter refer to, I construct the inner wall of the bottom of the furnace with a longitudinal channel I), preferably of semicircular or concaved form and uncovered at the top, so that the heat delivered Vthereto through the fuel'- inlet c in the back end of the furnace will be equally distributed over 4each crucible, the

flame and heat products whirling and circulating in the muffie and among the crueibles arranged therein. Sufficient pressure is thus generated in the muffle to force the flame or heat under the lower side edges of the muffle,

whence the flame or heat passes into the fluer tion, converges'toward the top of the furnace, 4

and the rear end of the muffie is designed to seat firmly against said projection, with anopening g in said end communicating with the space f', whereby cool outside air is caused to be drawn into the muffle during the process of cupellation, which is essential to the best results in this operation.

In connection with the muffle I employ when cupeling a removable bottom E for supporting the cupels L, said bottom being composed of fire-clay or equivalent material, and which removable bottom is supported at the sides and ends over bottom channel or iiue Z) by means of suitable blocks or projections e', formed on the bottom of the furnace, as shown in Figs. 3 and t, and which bottom and the front and rear ends of the furnace Inay be constructed as a rigid unitary structure, the front end having the usual door-controlled openingfor the insertion and removal of the'muffle.

The front opening is closed by a removable door F, composed of fire-clay or an equivalent heat-resisting medium, said door conforming to and closely fitting the opening, so that when the door is tightly closed the furnace will be practically air-tight; but when this door isy pulled out, say, a distance about equal to onehalf its thickness and which is represented by the projecting part l, of reduced diameter, which enters the open front end of the muffle, sufiicient outside air will be drawn in under the bottom of the door for cupellation purposes, while the door remains practically closed. This prevents the furnace from cooling, as it would necessarily do if the door were entirely removed.

When'the door is fully open, the draft induced in the furnace by the escape of the heat products through the outlet in the top of the. furnace causes fresh air to be drawn into the mouth or open front end of the mufiie.

In operation, as when melting in the crucibles, the removable bottom of muffle is dispensed with and heat is admitted to the muffle and circulates about the crucibles and finally escapes, as before pointed out. After the "melts have been poured the removable bottom of the muffle is placed in position, as before described and as shown in Fig. 1, and a little bone-ash is distributed around the i edges, thus making it tight, after which the furnace is ready for cupeling purposes.

Among the advantages which ow from the construction described are speed and capacity, for I find that I can do nearly double the work in a given time that I have been able to accomplish with other furnaces that I have used. Only about fifty per cent. of gasolene for fuel is required as compared with said other furnaces. My furnace is light and portable, and the heat is so nicely equalized that melts in front are ready to pour first, whereas in many other furnaces those at the rear must receive first attention, greatly to the inconvenience of the operator.

Another and decided advantage of my muffie over ordinary muffies is that its arrangement not only evenly distributes and utilizes all the heat, but it can be made at less cost and its life is many times prolonged, as the bottom, which is the destructible part of any muffle, does not receive any of the heat during melting in crucibles and can be made and replaced for a few cents if broken by accident. Also during operation all the heat is utilized inside, while the outside of the furnace is practically kept cool. Also less air-pressure is required than with the ordinary assay-furnaces.

Having thusdescribed my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. A muffle for an assay-furnace, said muffle having a separable bottom adapted to be detached from the mufi'le and removed through an opening in the furnace whereby said muffle is adapted for both melting' and cupeling operations. v

2. An assay-furnace, having a muffle-chamber and lmeans for admitting heat thereto, and

a muflie fitting the chamber' and havinga botfle-chamber and means for admitting a flame thereto, of a mufiie fitting said chamber and having its bottom open, and a normally disconnected readily-separable bottom fitting the opening in the bottom of the muflie and forming a removable closure therefor.

4. An assay-furnace comprising a base and ends and a body portion forming a mufflechamber, one of said ends having a projection on its inner face inclosing an air-space, amuffie in said chamber having an opening in its back end to connect said air-space with the interior of the mufiie, said muffle having a normally loose, readily separable bottom thereby adapting the muiiie for both melting and cupeling operations, means for admitting flame to the mufiie, and means whereby the spent products are allowed to escape from the furnace.

5. An assay-furnace having a base and ends and a connecting-shell, said shell includingan inner lining composed of heat-resisting material and forming a mufHe-chamber, a heat-resisting lagging surrounding the lining and an exterior metallic jacket, said base having a longitudinal open flue or channel into which heat is admitted and delivered directly into the muffle-chamber, and a removable muffle having a normally disconnected and readilyseparable bottom whereby the mufile is adapted for both melting and cupeling operations.

6. An assay-furnace comprising a base and ends and an arch-shaped body portion, said body portion having a fire-clay lining, an eX- terior metallic jacket, and an asbestos lagging between the lining and jacket, a muffie in the body portion and separated from said lining to form a passage for the escape of heat products, said mufiie having a bottom which is normally disconnected and readily separable from the main portion whereby the Inutile is adapted for both melting and eupeling operations, means for admitting' llame to the furnace, and means for admitting fresh aceretions of air to the mufiie-ehamber.

7. An assay-furnace comprising a base and ends and a shell or casing forming a mufflechamber, a muffle in said chamber and supported above the oor of the base, said muile having a false bottom which is normally disconnected and readily separable to permit the mufiie to be used for melting and cnpeling operations, an open-top iiue in the base below the mufie, and a door for closing the open nesses.

AMOS M. MACDUFFEE. Witnesses:

FRED yN. CHANDLER, EDWIN S. PoBEY. 

